This invention relates to molding compositions. In one of its aspects this invention relates to thermoplastic molding compositions. In another of its aspects this invention relates to a method for molding thermoplastic molding compositions using energy of microwave frequency. In still another aspect of the invention it relates to sensitizing thermoplastic molding compositions so that energy of microwave frequency can be used in the molding process. In yet another aspect the invention relates to objects molded of thermoplastic molding compositions.
It has been discovered as set out in copending application Ser. No. 825,175, filed Aug. 17, 1977 now U.S. Pat. No. 4,288,399, that microwave energy can be used to increase the temperature of polymer/resin compositions containing polar compounds so that the temperature is raised above the softening point and low pressure molding is possible. It has been found, however, that polar compounds useful in thermoplastic compositions used in low pressure moldings must be selectively chosen. Surprisingly, the discovery has been made that a sensitizer concentrate in the form of a free-flowing dry powder can be prepared which can be readily dry blended with other components to form a thermoplastic composition suitable for molding using microwave energy. The sensitizer concentrate contains polarizing agents along with other components to produce a free-flowing dry powder. Test results show that the use of a sensitizer concentrate provides better moldability than the separate addition of the sensitizer concentrate components under the same molding conditions and that the product of the molding exhibits greater transparency. Such characteristics greatly enhance the desirability of producing molded articles under low pressure (flow molding) conditions using microwave energy to obtain a variety of articles including laminates, foot wear, automobile mats, and the like.
It is therefore an object of this invention to provide sensitizer compositions which can be mixed with non-polar thermoplastic compositions to render the admixture susceptible to the heating effects of microwave energy so that the compositions will become softened. It is another object of this invention to provide a method for producing heat molding compositions containing non-polar thermoplastics by the addition of sensitizer concentrates to the thermoplastics. It is still another object of this invention to provide flow moldable compositions containing non-polar thermoplastic and sensitizer concentrates. It is still another object of this invention to provide molded objects produced from moldable compositions containing sensitizer concentrates.
Other objects, aspects and the various advantages of this invention will become apparent upon reading this application and the appended claims.